In making steel, a charge of pig iron, iron ore, and scrap steel can be melted in an electric arc furnace to produce a metal bath. Particulate lime or limestone is injected into the furnace, preferably early in the melting operation, to help form a slag over the surface of the metal bath to permit purification of the bath at a controlled rate. The placement of lime adjacent the electrodes of the furnace also tends to reduce wandering of the arc and decrease the noise level. When a suitable chemical analysis of the metal bath is achieved, deoxidizers such as ferrosilicon are added and the resulting steel is poured into molds and allowed to solidify.
Conventionally, lime is introduced into an electric arc furnace by introducing particulate lime into an airstream which is discharged through a duct in a side wall of the furnace. Since the lime must be introduced in a relatively short period of time, it impinges upon the carbon electrodes with sufficient velocity that it erodes or wears away portions of the electrodes, thereby significantly decreasing their useful life. Since the electrodes are massive and expensive, this erosion is costly and also increases the maintenance and down time of the furnace.
Since the opening of the duct is in the side wall of the furnace, the lime is not deposited uniformly in the center of the upper surface of the charge of metal in the furnace. Moreover, this opening is initially blocked by the charge of metal, and becomes cleared for use in introducing lime only after a substantial quantity of the charge has been melted to produce a metal bath. Therefore, in such a conventional furnace with a full charge of metal, lime cannot be introduced early in the melting operation, and purification at a slower rate and increased oxidation of the metal bath occurs.